1. Field of the Invention
The present invention relates generally to magnetic information storage devices, and more particularly to transducers for use in such devices. Still more particularly, the present invention relates to a thin film magnetic read/write head having a vertical magnetic gap and a method of fabrication therefor.
2. Description of Related Art
Magnetic disk drives are information storage devices which utilize at least one rotatable magnetic media disk having concentric data tracks defined for storing data, a read/write transducer for reading the data from or writing the data to the various data tracks, a support means, generally referred to as a slider, for supporting the transducer adjacent the data tracks typically in a flying mode above the storage media, a suspension assembly for resiliently supporting the slider and the transducer over the data tracks, and a positioning actuator coupled to the transducer/slider/suspension combination for moving the transducer across the media to the desired data track and maintaining the transducer over the data track center line during a read or a write operation. The transducer is attached to or is formed integrally with the slider which supports the transducer above the data surface of the storage disk by a cushion of air, referred to as an air bearing, generated by the rotating disk. Alternatively, the transducer may operate in contact with the surface of the media. The suspension provides desired slider loading and dimensional stability between the slider and an actuator arm which couples the transducer/slider/suspension assembly to the actuator. The suspension is required to maintain the transducer and the slider adjacent the data surface of the disk with as low a loading force as possible. The actuator positions the transducer over the correct track according to the data desired on a read operation or to the correct track for placement of the data during a write operation. The actuator is controlled to position the transducer over the desired data track by shifting the combination assembly across the surface of the disk in a direction generally transverse to the data tracks.
While magnetic recording of information is enormously successful, there is an ever increasing need to improve recording density. In the present state of the art the popular method of magnetic recording has been horizontal or longitudinal recording. In longitudinal recording, the magnetic polarity of the recorded bits is oriented horizontally or coplanar with respect to the recording medium surface. The magnetic flux from one of the pole tips of the write head passes through the magnetic storage medium horizontally downstream (or upstream), in reference to the direction of relative movement of the magnetic storage medium, to a return pole which forms the flux return path for the write head. The poles are separated by a gap which is made very small in order to `focus` the magnetic flux onto a small area of the magnetic medium at any one time during the write operation, thereby allowing a larger number of data bits to be recorded per lineal dimension along a data track. The width of the poles dictates the width of the data track and thus the number of data tracks that can be formed on the medium.
Needless to say, the thin gap between the magnetic poles must be precisely formed with the poles precisely aligned in order to improve the performance of the write head. To this end, the current state of the art offers several thin-film deposition approaches to fabricate the write head. These approaches all involve depositing multiple layers of magnetic and non-magnetic materials onto a substrate in selected sequences using vacuum deposition and/or plating techniques. The thin film heads so obtained are generally one of two types, namely those mounted with the thin film layers perpendicular to the magnetic medium and those mounted with the thin film layers parallel to the medium. For the former type of thin-film heads, typically two thin film magnetic pole layers are separated by a layer of gap material on a substrate. The fabrication process involves vertically cutting through the layers to expose and define the tips of the poles at the plane of the cut. A lapping step is therefore required to finish the pole tips which enhances the possibility of damage to the heads.
For the latter type of thin-film heads, a vertical wall which is perpendicular to the thin film layers separates the two poles, thereby defining the gap between the pole tips. One approach is to build the wall against the vertical edge of a pole layer and substrate, followed by joining a second substrate to the wall and forming a second pole layer across the wall opposite from the first pole layer. An example of such approach has been disclosed in U.S. Pat. No. 4,670,972 to Sakakima. This process has several drawbacks. First, a lapping step is required which enhances the possibility of damage to the heads. Second, alignment of the poles relies on the alignment limitation inherent in the photolithographic technique used in forming the poles in separate steps. Third, the requirement of joining two parts creates processing problems and does not facilitate batch processing on a wafer.
Another approach is to first build a free-standing wall, followed then by forming the magnetic poles on either side of the wall, as exemplified by U.S. Pat. No. 4,837,924 to Lazzari. U.S. Pat. No. 4,912,584 to Mallary discloses an approach to building a head adapted for mounting on the side of a slider, involving first building a free-standing wall on a substrate and then forming the poles.
Copending U.S. patent application Ser. No. 08/002,290 filed Jan. 8, 1993, commonly assigned to the assignee of the present invention, utilizes an approach involving first building a free-standing wall on a release layer which has been previously deposited on the substrate and then depositing the individual thin film layers of the head starting with the magnetic pole layers. The substrate is then removed by attacking i.e., dissolving, the release layer to leave the head or transducer with pole pieces exposed and separated by the wall. This process has been implemented in a so called "reed" approach to carry out batch production of the read/write head and the suspension as one integral unit. This is desirable for various reasons. In conventional disk drives, the transducer and the slider are formed separately from the suspension and then attached through an operator controlled precision operation. The parts are small and the positioning of each relative to the other must be exact. The transducer must be exactly positioned relative to the data track which in turn means that the suspension must be exactly positioned onto the slider. The suspension must provide flexibility and pitch and roll motion for the slider relative to the direction of motion of the rotating disk and yet provide resistance to the yaw motion. Any error in the placement of the suspension relative to the slider requires reattachment or can result in the scrapping of both pieces.
Once the suspension and the slider are correctly positioned, conductor leads must then be connected to the transducer. The conductor leads are directed along the suspension and connected to an amplifier placed on the suspension or otherwise attached to the actuator. The conductor leads must not add to the spring stiffness of the slider/suspension while yet providing good electrical interconnection. The conductor leads are generally bonded by soldering, for instance, to both the transducer output terminals and the amplifier by an operator. Again, assembly errors can cause scraping of the entire combination.
An integral construction using the reed approach to producing the transducer-slider-suspension alleviates some of the manufacturing concerns and permits the head and suspension to be easily and accurately manufactured in a batch process on an initial wafer surface.
The free-standing wall approaches utilized in the past are, however, not free from manufacturing difficulties. It has been experienced that the free-standing wall was fragile and not reproducibly self-supporting. This problem is exacerbated when the free-standing side wall is subject to the harsh environment of subsequent process steps which are carried out prior to formation of the magnetic poles, such as photoresist processing, etching and plating. In order to be able to survive subsequent processing, the structural integrity of the wall must be improved.